ORNITHORHYNCHUS. 



355 



state, but pieces of a substance resembling egg-shell 

 were picked out of the debris of the nest. In the 

 insides of several female Platypi which were shot, 

 eggs were found of the size of a large musket-ball, 

 and downwards, imperfectly formed, however, namely, 

 without the hard outer shell, which prevented their 

 preservation." 



That the ova of so small an animal as the ornitho- 

 rhynchus should equal the size of a large musket-ball, 

 before there is any appearance even of rudimental 

 organisation in them, is certainly different from what 

 occurs in placental mammalia of the same or even 

 greater size. But whatever may have been the size, 

 it is perfectly clear that they were not eggs in the 

 ordinary sense of the word, in which an egg means a 

 germ which, when matured, and still without even 

 the slightest development of organs, is entirely sepa- 

 rated from the parent animal, and developed by the 

 heat of that animal or of another, by artificial heat, or 

 simply by the natural heat of the ground, as it may 

 happen. The egg so produced contains in itself all 

 the essential elements of the animal, and wants neither 

 a supply of substance or of food from the mother. 



There are two stages in the process even here. 

 The germ, like the germs of all animals, has its 

 essential part formed in the ovary of the female ; and 

 though it descends into another vessel, in order to 

 be perfected, the chief additions which it receives 

 there are merely an increase of size, and the hard 

 external shell, by the maturing of which it appears 

 to be finally severed from its connexion with the 

 mother. But the largest germ which Lieut. Maule 

 found in the female ornithorhynchus, had no shell, or 

 firm external covering, by means of which it would 

 be preserved ; neither does it appear that it indicated 

 the slightest tendency to the formation of one. Re- 

 gular oviparous animals, or those which deposit their 

 eggs, so that they are hatched externally, always 

 produce them, if mature, with a firm covering. In 

 some, as in the shells of birds, this covering contains 

 a good deal of salts of lime ; whereas in other animals 

 it is more gelatinous, and in some it is flexible. In 

 all, however, it is of sufficient strength to protect its 

 contents from those casualties to which their external 

 situation would expose them ; and there are many 

 instances.in which, though the life of the animal pro- 

 ducing the egg is very easily destroyed, the egg 

 itself is durable beyond any known animal in the 

 organic state. 



In the second case, or in that of ovoviviparous animals 

 of which the only known vertebrated ones are either 

 reptiles or fishes, there is always an integument to the 

 egg, which cuts it off from all communication in sub- 

 stance with the body of the parent, as soon as it 

 comes to maturity. After this it merely receives, 

 within the body of its parent, that particular kind of 

 protection and stimulus which are necessary for its 

 development. Thus, though the situation and the 

 circumstances in which it is placed during the hatching, 

 differ in the oviparous and the ovoviviparous animal, 

 it appears that in the state of the egg itself, as indi- 

 cating a certain stage in the progress from the rudi- 

 mental germ to the fully developed animal, there is 

 scarcely any difference. 



Both from this analogy, and from the physiology 

 of the marsupial mammalia, it does therefore really 

 appear, that wherever the young of the ornithorhynchus 

 may receive its organic structure, it cannot with pro- 

 priety be called ovoviviparous, in the proper sense of 



the word, any more than it can be called oviparous, 

 as it has been done by those who fancied they got 

 possession of its eggs. The germs which have been 

 actually found in the female, whether of larger or 

 smaller size, have never been in a state for final sepa- 

 ration from the body of the mother, or even in the 

 slightest progress for being so separated, until some 

 organic development had taken place. 



To have a right understanding of the physiology 

 of this most singular of all mammalia, we must there- 

 fore, in the absence of certain information, which, 

 from the obscurity of the subject, is probably unat- 

 tainable, seek for our analogies in another quarter. 

 Now we find that in the kangaroos, and other typical 

 marsupial animals, which there have been opportuni- 

 ties of observing, the placental separation, if placenta 

 there be, in cases where no organ is distinctly 

 evolved by placental action, takes place before the 

 animal produced is capable of performing any one 

 animal function. But then, when discharged from its 

 internal lodgment, the rudimental animal is not in 

 such cases, hatched like an egg, by the application of 

 external stimuli operating upon it through an integu- 

 ment, which forbids the reception of any new matter. 

 The nipple is developed for its reception ; and a new 

 attachment, and direct communication of substance 

 by the parent to the young is established, and goes on 

 until it gradually passes into a supply of milk to an 

 animal tolerably perfect in its organisation, as is the 

 case in the common mammalia. In those marsupial 

 animals which have this type in their skeletons, but 

 which have the marsupium so little developed in 

 ordinary cases as to be incapable of receiving the 

 young, we know very little of the young when first 

 produced, for we are not aware of a single instance 

 in they have been found until so far developed as to 

 be able to cling to the mother and perform the ope- 

 ration of sucking. The absence of information with 

 regard both to the mother and the offspring, in this 

 stage of the process, is evidence that the conduct at 

 this time is obscure and concealed. The analogy 

 also points out, that it is to such animals that the 

 ornithorhynchus ought to point, in this particular stage 

 of its being. We know that placental mammalia come 

 into the world in very different states of development; 

 some so far advanced as to be able, in a very short 

 time, to move about, and partially to find their own 

 food. Others again are so backward in their develop- 

 ment, that if left to themselves they would inevitably 

 perish. 



If we find this difference among placental mam- 

 malia, none of which can be said to have anything 

 of a gestation external of the uterus, we may surely 

 be prepared to expect it in marsupial animals, the 

 process of whose development passes through a stage 

 more than the others. The state of the young orni- 

 thorhynchi, as found in the nest, tends to show that 

 when there they make a close approximation to the 

 young of the other marsupialia in the early stages of 

 their organic development. A description of the 

 young of this animal, abridged from an able exposition 

 by Richard Owen, Esq., one of our best and most 

 candid physiological anatomists, contains so many 

 particulars, bearing closely upon this most singular 

 and most mysterious point in animal history, that we 

 shall lay them before our readers, as they appear in 

 the proceedings of the Zoological Society of London, 

 a small work, but one in which an immense volume 

 of first-rate talent is concentrated. " The circum- 

 Z2 



